The present invention relates to apparatus for detecting activity of an animal heart. The apparatus has particular, but not exclusive, application in detecting activity of a human heart.
In an emergency in which a person has been rendered unconscious, either through accident or illness, one of the most crucial pieces of information required by a carer is whether or not the afflicted person""s heart is beating. If the person""s heart has stopped, suitable resuscitation measures must be taken as a matter of extreme urgency if brain damage is to be avoided. However, such resuscitation measures can be dangerous, and it is of importance that they are not applied to a person whose heart is still beating.
The traditional approach has been for a carer to feel for a pulse beat. To do this, the carer attempts to find a pressure point on the person""s body where arteries are close to the surface of the skin. A finger pressed against the arteries can then feel pressure pulses caused by blood being pumped by the heart.
Skill is required to perform this procedure reliably. The precise position of pressure points on a body varies from individual to individual. One locates a pressure point by probing with a finger until a maximum pulsation due to the heart pumping is felt. If the heart is beating faintly, a failure to locate precisely the pressure point could give the false impression of the heart having stopped. The clamour and confusion of an emergency situation makes this procedure all the more difficult. A carer is likely to be under stress, and will find it difficult to search diligently for an active pressure point, because his or her hands are shaking, because there is so much commotion at the site, or because his or her own heart beat pulsations are so strong that they mask those sensed on the patient""s body.
Moreover, the carer cannot undertake continual monitoring of the person while attending to other tasks. This gives rise to a risk that a deterioration in the person""s condition might go un-noticed.
An object of the invention is to provide apparatus which can accurately and reliably monitor a person""s heart activity in a form which can readily be used by a comparatively unskilled operator.
According to the present invention there is provided an apparatus for detecting heart activity of an animal heart comprising a housing within which is contained electronic circuitry, a power supply for the circuitry, and an indicator connected to the circuitry operable by the circuitry to generate an alerting signal detectable by a user, the apparatus further comprising a pair of sensors electrically connected to convey to the circuitry electrical signals detected by the sensors, the circuitry being operative to analyse signals received from the sensors and, upon determination that such signals are electrocardiographic signals derived from a heart beat, to cause the indicator to operate so as to generate an alerting signal.
Thus, while signals are being generated by the apparatus, the carer is reassured that the afflicted person""s heart remains active. If the signals should cease, or not issue upon application of the sensors to a person, this indicates that the person""s heart may have stopped and that immediate remedial action is required.
The indicator may issue visual signals (for example, it may be a light-emitting diode) or audible signals (it may be a sounder). Both of the aforementioned indicators may be provided, optionally in combination with additional indicators of any suitable type.
The housing may be of a type which permanently encapsulates components contained within it, and which is not intended to be opened subsequent to manufacture. This minimises the risk that the working parts of the apparatus will be subject to tampering.
The sensors may be in the form of electrodes and are preferably carried on wings extending from the housing. The wings are normally dimensioned to ensure that the electrodes are properly positioned when the apparatus is placed on a person""s chest. The wings are preferably not separable (other than by their destruction) from the housing. Most preferably, the wings are made from a flexible material so that they can be folded around or adjacent the housing for storage. The wings may be made from a conductive material, such as a conductive rubber, or they may have conductors embedded within them. Adhesive may be provided adjacent to the electrodes to enable them to be retained in contact with a person""s skin.
The circuitry preferably includes a switch, operative automatically to energise the circuitry upon detection of completion of a circuit between the electrodes. This causes the apparatus to start working automatically upon application on a person.
The circuitry preferably includes a rectification stage to ensure that the apparatus will operate irrespective of which electrode is placed upon one or other side of a person""s chest.
For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: